Optical monitoring chamber unit for toner density controls

ABSTRACT

A unit included in a toner density control (TDC) for electrostatic photocopiers incorporates an optical monitoring chamber, a filter chamber, and a venturi suction chamber for selectively introducing toner replenisher to a developer liquid pumped therethrough. A circuit board is detachably clamped to the unit and mounts a lamp and a pair of photocells in operative positions relative to the monitoring chamber.

United States Patent n 1 Hoffman 51 Mar. 27, 1973 OPTICAL MONITORINGCHAMBER UNIT FOR TONER DENSITY CONTROLS [75] Inventor: Lionel B.Hoffman, Wyckoff, NJ.

[7 3] Assignee: Pitney Bowes-Sage, lnc., Hawthorne,

[22] Filed: Apr. 7, 1971 [21] Appl. No.: 131,950

[52] US. Cl. ..l41/98, 95/89, 141/286, 141/325, 355/10 [51] Int. Cl...B65b 3/04 [58] Field of Search.95/89 AR, 89; 355/10; 137/386, 137/604;141/46, 95,113, 286, 285,100, 325, 98

[56] References Cited UNITED STATES PATENTS 3,354,802 11/1967 Doucetteet al ..95/89 AR 1,794,222 2/1931 Whitney ..95/89 AR PrimaryExaminer-Houston S. Bell, Jr. Attorney-William D. Soltow, Jr., Albert W.Scribner, Margin D. Wittstein and Louis A. Tirelli [57] ABSTRACT A unitincluded in a toner density control (TDC) for electrostatic photocopiersincorporates an optical monitoring chamber, a filter chamber, and aventuri suction chamber for selectively introducing toner replenisher toa developer liquid pumped therethrough. A circuit board is detachablyclamped to the unit and mounts a lamp and a pair of photocells inoperative positions relative to the monitoring chamber.

4 Claims, 3 Drawing Figures PATENTEDMARNIQI; 7 2,559

SHEET 1 [IF 2 INVENTOR LIONEL B. HOFFMAN ATTORNEY wnwm PATENTEDmznm v 3,559 sum 20F 2 INVENTOR I LIONEL B. HOFFMAN B M/wm ATTORNEY OPTICALMONITORING CHAMBER UNIT FOR TONER DENSITY CONTROLS BACKGROUND OF THEINVENTION In all electrophotographic systems, the toner concentrationsuspended in the developer medium must be replenished on same basis.Typically this is done automatically so as to not unduly burden theoperator. In some systems, toner replenishment is effected on aniterative basis. That is, after a predetermined number of copy cycles, apreselected arbitrary amount of toner concentrate or replenisher isautomatically added to the developer medium. This technique is simpleand economical to implement, however, it has the drawback in that thedepletion of the concentration is rarely uniform for each copy cycle orpredetermined number of copy cycles. Thus, it is not uncommon to developover a period of time a toner concentration which is outside of thelimits required for optimum copy quality. This situation can only berectified through manual intervention by the operator or servicepersonnel.

A more satisfactory technique, particularly in those electrophotographicsystems employing liquid developer, is to actually monitor on acontinuing basis the toner concentration or density, as suspended in theliquid vehicle, and to automatically initiate toner replenishment whenits concentration falls below a predetermined level. Since the degree oftoner concentration is directly proportional to the opacity of thedeveloper liquid, one of the most convenient ways in which to monitorthe toner density is optically. Such optical toner density controls(TDC) are well known and in wide use.

The typical practice is to continuously circulate the developer liquidthrough a monitoring chamber having transparent walls with a lightsource and a photosensor positioned on opposite sides of the chamber.The toner density of the developer liquid flowing through the chamberattenuates the intensity of the light beam incident on the photosensorand the proportional electrical response of the photosensor is processedpursuant to initiating toner replenishment when needed.

This technique works quite well until a highly light attenuating filminvariable builds up on the chamber walls to efficiently swamp the lightattenuating effects of the developer liquid, itself. The toner densitycontrol goes increasingly out of calibration and thus can no longerperform properly. The only recourse is to manually clean the monitoringchamber in order to remove the film buildup. This is a tedious task,requiring considerable time of trained photocopier service personnel. Atthe same time, the photocopier is out of service.

It is accordingly a general object of the present invention to provide aTDC monitoring chamber uniquely designed and incorporated into a lowcost, throwaway unit, which is readily demounted not for cleaning, butfor replacement typically on a periodic basis. A further importantobject is to provide in a single compact package of inexpensive design aunit which incorporates a TDC monitoring chamber, a filter chamber and aventuri suction chamber for introducing toner concentrate or replenisherto a developer liquid.

Other objects of the invention will in part be obvious and in partappear hereinafter.

SUMMARY OF THE INVENTION In accordance with the present invention, thereis provided a compact and inexpensive unit for incorporation in a tonerdensity control (TDC) included in an electrophotographic systemutilizing liquid developer, which unit provides the TDC opticalmonitoring chamber. Moreover, the unit combines with the TDC monitoringchamber in a single package, a filter chamber and a venturi suctionchamber of simplified design. The unit is of such low cost that itbecomes eminently practical to simply periodically replace it entirely,rather than to expend the time and effort to periodically clean it. As aresult the load on the manufacturers service personnel is lightened andcopier down time is reduced.

The disposable unit of the present invention is detachably mounted tothe developer tank of a liquid development station. An inlet to thefilter chamber is coupled to the outlet of a liquid developercirculating pump whose intake is submerged in the developer bath. Thefilter chamber includes a filter screen through which the developerliquid flows as it is pumped therethrough. The filter chamber opens intothe monitoring chamber which accepts developer liquid flow therefrom. Acircuit board carrying various electrical components required in thetoner density control is detachably clamped to the unit. Among thecomponents mounted by the circuit board are a lamp and a photosensor,which are automatically positioned on opposite sides of the monitoringchamber incident to clamping the circuit board to the unit. The lampbeams light through the transparent sidewalls of the monitoring chamberand the developer liquid flowing therethrough to the photosensor,pursuant to monitoring the developer liquid opacity.

From the monitoring chamber, the developer liquid flows through anorifice and back into the developer tank. In accordance with a featureof the invention, the orifice is constituted by an elongated eyeletmounted concentrically within a sleeve which serves as a suction chamberwhose outlet is coupled back into the developer tank. In advance of thedischarge end of the eyelet, the sleeve is formed with a pair of inlets.One of these inlets is coupled to a supply of toner concentrate orreplenisher mounted by the developer tank. The other inlet isselectively vented. As the developer liquid discharges from the eyeletfor return to the developer tank, a negative pressure is created in thearea between the eyelet and the sleeve adjacent the two inlets. So longas the second inlet is vented, air is brought in to satisfy thisnegative pressure in preference to the heavier toner concentrate.

On the other hand, when the opacity of the developer liquid flowingthrough the monitoring chamber decreases below a predetermined level,indicating a depletion of the toner concentration therein, the resultingelectrical response of the photosensor is used to initiate actuation ofsuitable means, such as a valve, which closes off this second inlet. Thenegative pressure condition is sufficient to draw toner concentrate fromthe supply which is combined with the developer liquid discharging fromthe eyelet.

The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the inventionreference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a fragmentary, perspective view of a liquid developmentstation incorporating a disposable unit constructed according to apreferred embodiment of the invention;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1; and

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2.

Like reference numerals refer to corresponding parts throughout theseveral views of the drawings.

DETAILED DESCRIPTION Referring to FIG. 1, the disposable unit of thepresent invention, generally indicated at 10, is made of a suitabletransparent plastic and is supported in an upright position on a deck 12secured to a developer tank 14 located at a liquid development stationof an electrophotographic copier. A pump 16 has an intake (not shown)submerged in the developer bath contained by developer tank 14 and adischarge 18 which is coupled by conduit 20 to an inlet sleeve 22 ofunit the inlet sleeve extending downward through an opening 24 in deck12 (FIG. 3). Hose clamps 26 secure the ends of conduit 20 on the pumpdischarge l8 and the inlet sleeve 22. As best seen in FIG. 3, the hoseclamp 26 clamping the end of conduit-20 on the inlet sleeve 22 ispositioned immediately below deck 12 and thus serves to detachablysecure unit 10 in an upright position on the deck.

As best seen in FIG. 3, inlet sleeve 22 opens into a verticallyelongated filter chamber 30 of rectangular cross section. A mesh filterscreen 32 in the form of an inverted V is accommodated in filter chamber30 to screen out conglomerates as the developer liquid is pumpedupwardly through the filter chamber. A portion of the upper end offilter chamber 30 is terminated by horizontal ledge 34 (FIGS. 1 and 2).This ledge 34 is formed having an elongated surface groove 36accommodating the shank of a bolt 37 which is passed through an aperturein a circuit board 38. A recess 40 intersecting groove 36 captures a nut41 in which bolt 37 is threaded to clamp circuit board 38 to unit 10. Asseen in FIG. 3, the lower edge of circuit board 38 rests on a ledge 42extending from the lower end of sidewall 44 for filter chamber 30.

The remainder of the upper end of filter chamber 30 laterally of ledge34 opens into a monitoring chamber 50 bounded in part by upperextensions of the filter chamber sidewalls and a cover 52. As best seenin FIG. 2, the circuit board 38 mounts a lamp 54 and a photosensor, suchas a photocell 56, which, when the circuit board is clamped to unit 10,are positioned on opposite sides of the monitoring chamber 50. The lightfrom lamp 54 is transmitted through opposed chamber sidewalls 58 and 60and the developer liquid to photocell 56.

Still referring to FIG. 2, unit 10 is provided with a support wall 62which serves to mount a window 64 on the opposite side of lamp 54 frommonitoring chamber sidewall 58. Mounting wall 62 is extended beyondwindow 64 to provide a ledge 62a, while the lower edge of the window isformed having a horizontally extending ledge 64a which serves incooperation with ledge 62a and circuit board 38 to mount a sheet 66 ofoptical filter material on the opposite side of the window from lamp 54.A second photocell 68 is mounted by resilient electrical leads 68a tothe circuit board 38. The springy leads 68 serve to resiliently urge theface of photocell 68 against window 64, thus to clamp the filter sheet66 therebetween.

The provision of a second photocell in a toner density control is oftenresorted to in the field to afford compensation for variations in thelamp light output, while the optical filter 66 is utilized to establishan opacity standard for the developer liquid flowing through themonitoring chamber 50. Applicant does not claim any invention in -theuse of the second, compensating photocell 68 or the use of an opticalfilter to establish an opacity standard. Applicants invention is howeverconcerned with the design of unit 10 to accommodate second photocell 68and the optical filter 66.

As seen in FIGS. 2 and 3, sidewall 70 of the filter and monitoringchambers terminates short of cover 52 to provide a laterally extendingpassageway 72 accommodating the flow of developer liquid from themonitoring chamber. The floor 74 of this passageway 72 is formed havingan opening 74a in which is fitted an elongated eyelet 76, formed ofmetal, for example. De-

. pending from floor 74 concentrically about eyelet 76 is an elongatedsleeve 78, which, as will be seen serves as a suction chamber. Thedeveloper liquid passing from the monitoring chamber 50 throughpassageway 72 flows downwardly through the restricted orifice affordedby eyelet 76. A hose 80, inserted on the lower end of sleeve 78, extendsthrough an aperture 81 in deck 12 to return the developer liquid to tank14.

Sleeve 78 is provided with a pair of inlets 82 and 84 communicating withthe interior of the sleeve at a level above the discharge end of eyelet76. Inlet 82 is connected by a hose 86 to a valve 88 (FIG. 1), whileinlet 84 is coupled by a hose 89 to a supply of toner concentrate orreplenisher held in a container 90. Normally valve 88 is conditioned bythe toner density control to vent inlet 82 to the atmosphere. Thus, thevacuum created by the flow of developer liquid from the small bore ofthe eyelet 76 into the larger bore of sleeve 78 causes air to be drawnin through inlet 82. However, when an addition of toner concentrate tothe developer liquid is called for by the toner density control, valve88 is actuated to close off inlet 82 and thus the vacuum created in thearea between eyelet 76 and sleeve 78 is sufficient to draw tonerconcentrate from container 90.

The toner concentrate enters through inlet 84 and is its entirety ratherthan to clean the film buildup from the monitoring chamber walls inorder to re-establish proper TCD operation. To replace unit 10, bolt 38is removed to demount-the circuit board 38. It will be noted that as thecircuit board is moved aside, it carries with it the two photocells andlamp 54. Deck 12 is detached by removal of screws 13 and lifted fromdeveloper tank 14 to provide access to hose clamp 26 for disconnectionof the conduit 20 from the intake sleeve 22. After the disconnection ofhoses 86 and 89, the unit is completely freed for removal andreplacement.

It is also seen that the unit is of extremely compact design with themonitoring chamber mounted atop the filter chamber and the suctionchamber or sleeve 78 depending from passageway 72 laterally extendedfrom the monitoring chamber. Thus, the flow path for the developerliquid is folded on itselfin an inverted U- shaped configuration,occupying very little horizontal surface area of tank 14.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

l. A disposable combined toner optical monitoring and toner concentrateinjecting device for use in an electrophotographic liquid developingsystem including a tank of liquid developing toner and a circulatingpump located in the tank, said device comprising:

A. a unitary, generally elongate and vertically oriented housing beingremovably supported by a portion of the toner tank,

B. wall means forming a portion of said housing to define a firstvertical passageway extending substantially the height of said housingthrough which toner in the tank is adapted to pass, at least a portionof said first vertical passageway being formed of transparent materialand defining a monitoring chamber for permitting optical monitoring theopacity of toner passing therethrough, the lower I end of said firstvertical passageway having means removably connected to an outlet of thepump in the toner tank,

C. additional wall means of said housing defining a lateral passagewaycommunicating at one end with the upper end of said first verticalpassageway,

D. further additional wall means of said housing defining a secondvertical passageway which communicates with the other end of saidlateral passageway, the lower end of said second vertical passagewaybeing adapted to communicate with the interior of the toner tank wherebytoner in the tank is pumped through said first vertical passageway, saidlateral passageway and said second vertical passageway back into thetank without passing outside of said housing,

E. means in said vertical passageway defining a restricted orificethrough which the toner passes to form a suction chamber in said secondvertical assagewa ad'acent said orifice, F. :neans defiiiing a firstinlet to said suction chamber and adapted to be normally connected toatmosphere for venting said suction chamber, and

G. means defining a second inlet to said suction chamber and adapted tobe connected to a source of toner concentrate whereby toner concentrateis drawn into said suction chamber through said second inlet andinjected into the toner passing therethrough when said first inlet isblocked to prevent the venting of said suction chamber.

2. A device as set forth in claim 1 wherein another portion of saidfirst vertical passageway beneath said first portion defines a filteringchamber and there is further included in said disposable device a meshscreen filter in said filtering chamber for filtering toner passing intosaid monitoring chamber.

3. A device as set forth in claim 1 wherein said means defining saidrestricted orifice comprises an elongate eyelet mounted in one of thewall means defining said second vertical passageway, said eyeletcooperating with said wall means defining said second verticalpassageway to define said suction chamber therebetween.

4. A device as set forth in claim 1 wherein said housing includesadditional wall means defining an open chamber located laterallyadjacent said monitoring chamber for accommodating a lamp and alsoforming support for an opticalfilter in spaced relation with saidmonitoring chamber on the side of said open chamber remote from saidmonitoring chamber, whereby a lamp placed in said open chamber canproject light in opposite directions through an optical filter mountedon said support and through toner passing through said monitoringchamber.

1. A disposable combined toner optical monitoring and toner concentrateinjecting device for use in an electrophotographic liquid developingsystem including a tank of liquid developing toner and a circulatingpump located in the tank, said device comprising: A. a unitAry,generally elongate and vertically oriented housing being removablysupported by a portion of the toner tank, B. wall means forming aportion of said housing to define a first vertical passageway extendingsubstantially the height of said housing through which toner in the tankis adapted to pass, at least a portion of said first vertical passagewaybeing formed of transparent material and defining a monitoring chamberfor permitting optical monitoring the opacity of toner passingtherethrough, the lower end of said first vertical passageway havingmeans removably connected to an outlet of the pump in the toner tank, C.additional wall means of said housing defining a lateral passagewaycommunicating at one end with the upper end of said first verticalpassageway, D. further additional wall means of said housing defining asecond vertical passageway which communicates with the other end of saidlateral passageway, the lower end of said second vertical passagewaybeing adapted to communicate with the interior of the toner tank wherebytoner in the tank is pumped through said first vertical passageway, saidlateral passageway and said second vertical passageway back into thetank without passing outside of said housing, E. means in said verticalpassageway defining a restricted orifice through which the toner passesto form a suction chamber in said second vertical passageway adjacentsaid orifice, F. means defining a first inlet to said suction chamberand adapted to be normally connected to atmosphere for venting saidsuction chamber, and G. means defining a second inlet to said suctionchamber and adapted to be connected to a source of toner concentratewhereby toner concentrate is drawn into said suction chamber throughsaid second inlet and injected into the toner passing therethrough whensaid first inlet is blocked to prevent the venting of said suctionchamber.
 2. A device as set forth in claim 1 wherein another portion ofsaid first vertical passageway beneath said first portion defines afiltering chamber and there is further included in said disposabledevice a mesh screen filter in said filtering chamber for filteringtoner passing into said monitoring chamber.
 3. A device as set forth inclaim 1 wherein said means defining said restricted orifice comprises anelongate eyelet mounted in one of the wall means defining said secondvertical passageway, said eyelet cooperating with said wall meansdefining said second vertical passageway to define said suction chambertherebetween.
 4. A device as set forth in claim 1 wherein said housingincludes additional wall means defining an open chamber locatedlaterally adjacent said monitoring chamber for accommodating a lamp andalso forming support for an optical filter in spaced relation with saidmonitoring chamber on the side of said open chamber remote from saidmonitoring chamber, whereby a lamp placed in said open chamber canproject light in opposite directions through an optical filter mountedon said support and through toner passing through said monitoringchamber.